Here's my take on this subject after owning a few pairs. Taking care of them, is going to be your best way to keep them usable. Some $10 waders will last as long as some $300 ones. Hang them after every use, so they don't grow any mold. When taking them off, stand on a piece of carpet or tupperware lid (so you are not stepping on gravel). Try to be gentle taking them off and on, if they are not pulling right off, don't stress the seems. Sit down on your bumper, and rock your foot loose. Wash them per instructions, every good 20-30 uses. If yours are anything like mine, there are fish scales and blood all over, which are going to attract fungus.
If the way you treat them is equal, then here is my suggestion.
Gore Tex are likely going to last the longest. They are strong and breathable, and have products out, that will restore the water repelency (Nik Wax). This didn't seem to work on a pair of Cabela's that I had, which were their highest line when I bought them 10 years ago. Another bonus of Gore Tex, is most companies that use Gore Tex in their waders, have a great warranty. Simms, LL Bean, and even Cabela's will replace 2 year old leaky waders.
That being said, a properly maintaned set of $70 waders, should last you 2-3+ years. A properly mantained set of $200 Gore Tex waders should last you about 5-6+ years. Money wise, the $70 would likely be a better deal, but you never know when they are going to decide to start leaking. Nothing like being on the Erie tribs when it is 25 degrees, and you feel that slow leak starting. Gore Tex, you can "recharge" them and ready to roll in about an hour. The $70 brand forces you to drive around to the local shops, likely paying an extra 20% on a pair of waders to get you through your trip.
A second pair of waders is always a good idea. I like the cheap canvas/rubber Gander Mountain brand with the built in boots. Work really good for the ocean, when it is cold. Keeps the sand out of your shoes, and doesn't put the beating of the salt on your good waders (rinse after every use). They serve their purpose, if your other waders spring a leak. You'll sweet like crazy in the summer with them though, just like the neoprenes. Neoprenes are great for cool weather fishing. They are a little uncomfortable, for long hikes though. They are a better option than my spare pair, for comfort though. So if you have them as your back up set, then you are good to go.